1. Field of the Invention
The present invention relates in general to envelopes, especially those having pressure sensitive adhesive flaps. In particular, the present invention relates to an improved envelope having a reusable adhesive flap, and a method and apparatus for making same.
2. Description of the Related Art
Typical envelope configurations include a pouch section adapted to receive the contents of the envelope, and a flap located at the opening of the pouch and adapted to be folded over and secured to the exterior of the pouch. While it has been known for some time to provide the flap with an adhesive, in recent years it has become increasingly common to provide a pressure sensitive adhesive, so that moistening of the adhesive is not required.
Certain envelope types, such as those intended for interoffice communications, are used numerous times before being discarded. Such envelopes have been known to be provided with a string-and-post closure arrangement to secure the flap in the closed position. With the increased use of pressure sensitive adhesive seals, it has been desired to provide interoffice-type reusable envelopes having adhesive flaps. To permit this, however, it is often desirable to provide the pouch exterior with a protective area to which the adhesive will adhere. Such a protective area will help to ensure the pouch body material does not delaminate and destroy the envelope, and/or the fibers from the pouch body will not build up on tile adhesive to reduce its bond strength.
One commercially available envelope of this type employs a protective strip in the form of a first adhesive tape adhesively secured to the exterior of the pouch. The flap includes a large aperture, and a length of a second adhesive tape is secure to the exterior of the flap, over the aperture. The portion of the second adhesive tape within the aperture may then be secured to the protective strip upon closing the flap. The protective strip has a stronger bond to the pouch than to the adhesive tape, and as such the tape may be removed from the protective strip to allow the envelope to be opened and reclosed many times.
While this arrangement is serviceable, it does have several drawbacks. First, the envelope blank must undergo a separate step to form the aperture in the flap. Second, the protective strip and adhesive tape must be applied in two separate steps, with folding of the flap taking place between these steps. Finally, the flap is secured in the closed position during manufacture. As such, the user must break the adhesive seal prior to the first use of the envelope, reducing user confidence in the seal.
It has also been known to place a strip of adhesive tape upon the interior of the flap, with the adhesive tape being initially covered by a release layer. This arrangement prevents the flaps from sticking to other envelopes, provides a strong initial seal, and avoids the need to close the flap to add the flap tape. However, these strips of tape are applied parallel to the flap fold. In most envelope forming processes the envelopes are transported perpendicular to the flap fold. As such, these adhesive tapes must be applied as a separate step by a separate machine.